Fragility behavior of melamine formaldehyde three dimensional network

By calorimetric investigations, the variations of the heat capacity Delta C -p = [C-pl - C-pg](T=Tg) at the glass transition and the fragile index (m), of a cured (85 degrees C for 20 h) melamine formaldehyde resin were determ ined. The calculated value Delta C-p = 0.13 J g(-1) K-1 and m = 143, lead t o conclude that the resin exhibits a 'strong' thermodynamic behavior and a 'fragile' kinetic behavior. Compared with those of the literature on three- dimensional networks and on inorganic polymers, our results allow us to pro pose that relaxation occurs in these systems mainly by movements involving triazine rings. (C) 2000 Elsevier Science B.V. All rights reserved.